Variable bit rate audio information transmitting apparatus, and method therefor

Abstract

A variable bit rate audio information transmitting apparatus, and a method therefor, are disclosed in which a bit rate is properly increased or decreased in accordance with the amount of audio information and by taking a fixed bit transmitting rate as a reference, so that the data rate can be adjusted in accordance with the importance of the audio information. The data bit amount of the currently inputted frames are computed to compare with a fixed bit allocation amount, and surplus bits and dummy data are properly allocated to the compared result, so that the bit amount allocated to the inputted data amount can be varied in transmitting the signals. The bit distribution is efficiently carried out through bit amount variation adjustment in accordance with the amount of sound source. Therefore the sound quality is improved, the deterioration of the sound quality is reduced, and the audio data is reduced. Further, the amount of the dummy data is reduced within the bit stream so that the bit utilization can be improved.

What is claimed is: 
     
       1. A method for transmitting variable bit rate audio information with video information, comprising the steps of: computing a first bit allocation amount for the audio information for a current frame;   comparing the first bit allocation amount with a second fixed bit allocation amount to obtain a compared result, the comparing step further comprising outputting the compared result on a first output line connected between a comparator and a bit rate adjuster when the first bit allocation amount is greater than the second fixed bit allocation amount and outputting the compared result on a second output line connected between the comparator and the bit rate adjuster when the first bit allocation amount is less than the second fixed bit allocation amount;   allocating to the current frame an effective bit rate allocation and dummy data based on the compared result, the step of allocating the effective bit rate allocation and the dummy data comprising a) accumulating a difference value to obtain a final surplus bit amount if said difference value is outputted through the first output line of the comparator, and computing said final surplus bit amount by subtracting said difference value from an accumulated value if said difference value is outputted through the second output line of the comparator,   (b) checking whether a value of said surplus bit amount of step a) is larger than a user defined value smaller than said second fixed bit allocation amount,   c) storing said surplus bit amount minus said user defined value into a dummy variable so as to compute dummy data if said surplus bit amount is equal to or larger than said user defined value, and replacing a surplus bit variable with said user defined value, and   d) computing an effective bit allocation amount to be allocated to the current frame by adding said surplus bit amount to said second fixed bit allocation amount so as to carry out a bit allocation if said surplus bit amount is smaller than said user defined value, and outputting current frame data to a formatting device so as to be formatted; and     encoding and transmitting the audio and video information;   whereby the effective bit allocation is varied in accordance with inputted audio information amount relative to a fixed amount.     
     
     
       2. A variable bit rate audio data transmitting apparatus for transmitting video and audio data, comprising: a video buffer for storing inputted video data for a current frame;   a bit allocation processor for providing a first bit allocation amount to compress inputted audio data for the current frame;   a varying device for comparing the first bit allocation amount with a second fixed bit allocation amount to obtain a compared result and for varying an effective bit rate allocation depending on the compared result;   a formatting device for formatting output audio data of said bit allocation processor and said varying device to a system output format; and   an encoder for encoding video data of said video buffer and audio data of said formatting device;   said varying device including a counter for counting the first bit allocation amount for the current frame, a reference bit rate device for outputting the second fixed bit allocation amount, a comparator for comparing the first and second bit allocation amounts to obtain the compared result, a bit rate adjuster for computing a dummy data amount and effective bit rate allocation, and a dummy data counter for storing dummy data from said bit rate adjuster and for outputting to said formatting device;   wherein first and second output lines communicate between said comparator and said bit rate adjuster, said first output line being used when the first bit allocation amount is greater than the second fixed bit allocation amount and said second output line being used when the first bit allocation amount is less than the second fixed bit allocation amount and effective bit rate allocation is varied depending on the compared result of first and second bit allocation amounts so that greater or lesser amounts of audio data can be encoded with the video data of said current frame.